Re: [Qemu-devel] [PATCH v3 02/20] virtio: pci-legacy: Validate queue pfn

[Michael S. Tsirkin]

On Fri, Jun 29, 2018 at 12:15:22PM +0100, Suzuki K Poulose wrote:
> Legacy PCI over virtio uses a 32bit PFN for the queue. If the
> queue pfn is too large to fit in 32bits, which we could hit on
> arm64 systems with 52bit physical addresses (even with 64K page
> size), we simply miss out a proper link to the other side of
> the queue.
> 
> Add a check to validate the PFN, rather than silently breaking
> the devices.
> 
> Cc: "Michael S. Tsirkin" <address@hidden>
> Cc: Jason Wang <address@hidden>
> Cc: Marc Zyngier <address@hidden>
> Cc: Christoffer Dall <address@hidden>
> Cc: Peter Maydel <address@hidden>
> Cc: Jean-Philippe Brucker <address@hidden>
> Signed-off-by: Suzuki K Poulose <address@hidden>
> ---
> Changes since v2:
>  - Change errno to -E2BIG
> ---
>  drivers/virtio/virtio_pci_legacy.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_pci_legacy.c 
> b/drivers/virtio/virtio_pci_legacy.c
> index 2780886..c0d6987a 100644
> --- a/drivers/virtio/virtio_pci_legacy.c
> +++ b/drivers/virtio/virtio_pci_legacy.c
> @@ -122,6 +122,7 @@ static struct virtqueue *setup_vq(struct 
> virtio_pci_device *vp_dev,
>       struct virtqueue *vq;
>       u16 num;
>       int err;
> +     u64 q_pfn;
>  
>       /* Select the queue we're interested in */
>       iowrite16(index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
> @@ -141,9 +142,15 @@ static struct virtqueue *setup_vq(struct 
> virtio_pci_device *vp_dev,
>       if (!vq)
>               return ERR_PTR(-ENOMEM);
>  
> +     q_pfn = virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT;
> +     if (q_pfn >> 32) {
> +             dev_err(&vp_dev->pci_dev->dev, "virtio-pci queue PFN too 
> large\n");
> +             err = -E2BIG;

Same comment here. Let's make it clear it's host not guest problem.

> +             goto out_del_vq;
> +     }
> +
>       /* activate the queue */
> -     iowrite32(virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT,
> -               vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
> +     iowrite32(q_pfn, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
>  
>       vq->priv = (void __force *)vp_dev->ioaddr + VIRTIO_PCI_QUEUE_NOTIFY;
>  
> @@ -160,6 +167,7 @@ static struct virtqueue *setup_vq(struct 
> virtio_pci_device *vp_dev,
>  
>  out_deactivate:
>       iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
> +out_del_vq:
>       vring_del_virtqueue(vq);
>       return ERR_PTR(err);
>  }
> -- 
> 2.7.4